The traditional method of olefin production is the cracking of petroleum feedstocks to olefins. The cracking of petroleum feedstocks is done through catalytic cracking, steam cracking, or some combination of the two processes. The olefins produced are generally light olefins, such as ethylene and propylene. There is a large market for the light olefin products of ethylene and propylene. As petroleum feedstocks from crude oil face increasing prices it is advantageous to provide for other sources of ethylene and propylene. It is also known that olefins can be produced from oxygenates. The most common conversion of oxygenates to olefins is the production of light olefins from methanol, wherein methanol can be produced from other sources, including biomass, and natural gas.
The process of converting oxygenates to olefins is an important process for utilizing oxygenates, such as methanol, and converting them to higher value products such as monomers for plastics, such as ethylene and propylene. The process of converting oxygenates to olefins is a catalytic process, and the catalyst is usually a molecular sieve catalyst. Among the molecular sieves that are useful for the catalytic process are ZSM-type molecular sieves, but more particularly, it has been found that silico-aluminophosphate (SAPO) molecular sieves work well in the process.
SAPOs are synthesized by forming a mixture containing sources of silicon, aluminum, and phosphorus mixed with an organic template, and then crystallizing the molecular sieve at reaction conditions. Many factors affect the form the molecular sieve takes, including the relative amounts of the different components, the order of mixing, the reaction conditions, e.g. temperature and pressure and the choice of organic template.
However, MTO catalysts are expensive and susceptible to erosion. The erosion creates catalyst fines that are carried out in the MTO reactor effluent stream. The catalyst fines create a problem for downstream equipment.